Figure 5.

Neurites in Neuro-2a cells exhibit dynamic behaviors. A, Growth cone dynamics in MAP2c-transfected Neuro-2a cells. Simultaneous DIC and fluorescence imaging of a GFP-MAP2c-transfected cell revealed the rapid formation of a growth cone-like structure (large arrows) at the tip of a newly formed neurite (also see Fig 5.mov; time points represent hours:minutes). On encountering a nonpermissive substrate (a scratch in the surface of the coverslip), the growth cone structure collapsed, and the neurite retracted rapidly, showing morphological characteristics of those in primary neurons, including a retraction bulb (arrowhead) and trailing membrane remnants (small arrow). B, Rapid bundling of MAP2c-decorated microtubules during process formation. Shown is a magnified view of the boxed portion of A. During the first 5 min, a short protrusion containing a few unbundled MAP2c-decorated microtubules was formed (arrowhead). During the next 10 min, the microtubules quickly formed a packed array to produce a transient, neurite-like structure.